Reliance on so-called offshore techniques is increasing when extracting natural resources from the earth, and as a consequence, deeper and deeper sources of crude oil are being exploited by deep sea drilling, sometimes at depths far greater than 1,000 m.
In particular, the events on the drilling platform “Deepwater Horizon” have shown that this type of deep sea drilling is connected with high levels of danger and that it is difficult to seal boreholes from which a fluid, in particular, crude oil, discharges uncontrolled. For one, the great depth makes the sealing work generally difficult. For another, the oil often gushes out of the borehole at high pressure, so that it is not even possible to seal the borehole in one step even with a massive dome.
As a rule, known methods for sealing boreholes are, as described, for example, in European patent specification EP 1067758 B1, are designed for sealing ordinarily formed test boreholes and not suitable for sealing a larger hole from which crude oil gushes uncontrolled.
Keeping larger devices on hand with which even large holes can be sealed securely is hardly possible, because of the required size for such, for example, a dome, and would incur immense costs.